However his work has been admired, studied and analyzed by "Tolkienists" over the years in various aspects and levels; unavoidably, some more or less obvious inconsistencies seem to have slipped the author's attention. Most are revealed after more than one reading of the book and possibly thorough study.

Fans of Tolkien usually accept that in any work there are usually plot holes. In a larger, far more detailed and realistic book we expect fewer (if any) plot holes, when in reality there is a far greater chance because of its complexity.

Any inconsistency can be blamed on the fictitious Tolkien who adapted ancient sources such as the Red Book or on the characters who wrote and compiled those sources. Tolkien himself mentioned in Appendix D that he might have made many errors on the calendar while "translating" the "ancient sources", a comment written as a fail-safe for any narrative mistakes the author might have made, and mentioned in Appendix F ("Of the Elves") that Frodo had erred in thinking the dialect of Sindarin spoken by the elves of Lórien was Silvan Elvish.[1]

Such explanations attributing the mistakes to the "translator Tolkien" or the "original sources" are easy and unenlightening. Therefore many fans prefer to explain those inconsistencies with some internal explanation. The explanations below of are this type. For example, at least some of the logical mistakes can be attributed to the characters themselves who said a contradicting phrase, since none of them is supposed to have the "omniscience" of the author. Contradictions of this type are grouped as "character mistakes". Others are grouped as "factual mistakes", of which mistakes in chronology are a subgroup.

Maybe Tom is not "alive" as Treebeard is[6] (though he seems to be). On this subject, Gandalf, Saruman, and Sauron have existed far longer than Treebeard, as they are Maiar, but they haven't been alive (in a physical body) as long.

Sam's spying

Merry tells Frodo that as a result of Sam's eavesdropping, he and Pippin "know most of what Gandalf has told you about the Ring".[7] Most of what Gandalf told Frodo was in one long conversation, at the end of which Gandalf caught Sam.[8] This contradicts Merry's statement that after Sam was caught, he "seemed to regard himself as on parole, and dried up".[7]

Explanation

Maybe Sam's information was what he learned before he was caught, though that's not what Merry says.

A choice of dangers

Aragorn tells the hobbits, as they prepare to leave Bree, "After Weathertop our journey will become more difficult, and we shall have to choose between various dangers."[9] The ridges they have to climb after Weathertop may be more difficult than the Midgewater Marshes, but they encounter no dangers on the route Aragorn chooses, and Aragorn doesn't warn the hobbits of any dangers, except the chance that the Nazgûl will find them as they cross the Last Bridge.[10]

Explanation

Aragorn does cite two other possible courses. One is going north through the Ettendales instead of crossing the Ford of Bruinen, but in addition to the danger of trolls, that route would take too long and the Company would run out of food. The other is finding the Ford without following the Road, but that's impossible.[11] Maybe although he describes these alternatives as impossible when he faces them, in Bree they only seemed to present the danger of taking too long or getting lost.

Aragorn's knowledge

Aragorn tells the hobbits in Bree, "I know all the lands between the Shire and the Misty Mountains, for I have wandered over them for many years."[9] But later, speaking of the Ettendales, he says, "That is troll-country, and little known to me," and "I do not know the way" to Rivendell by detouring through them.[10] The Ettendales or Ettenmoors are on a line between the Shire and the northern part of the Misty Mountains.

Explanation

If we take Aragorn's line "wandered over them" literally, we can accept that Aragorn has also wandered over the Ettendales. Of course that doesn't necessarily means that Aragorn should know everything about those lands, or even know all ways (e.g., to Rivendell) through them. He does say that he knows those lands a "little".

In The Council of ElrondGandalf says that the Nazgûl kept their Rings by saying "The Nine the Nazgûl keep"[3]. However in most other references, it is mentioned that Sauron had taken them.[12][13] Furthermore, Frodo doesn't see any Rings on them on Weathertop, and it is believed that if they did wear the Rings, they would have been fully invisible (including their cloaks).[14]

The line in the Council of Elrond represents Tolkien's earlier intention that the Nazgûl should still be wearing their Rings, but he later changed his mind and simply missed revising that sentence.

Explanation

The phrase can be also interpreted as "The Nine keep the Nazgûl [in Sauron’s thralldom]"; or as the Nazgûl are Sauron's slaves, his owning the Rings may be equivalent to the Nazgûl's keeping them.

The mithril coat that Bilbo gives Frodo is "almost as supple as linen",[15] and Aragorn carries Frodo in Moria (after the orc chieftain spears Frodo) without noticing the coat.[16] However, when Bilbo slaps Frodo on the back after giving him the coat, he says, "Ow!... You are too hard now to slap!"[15]

Explanation

Perhaps Bilbo is joking.

Galadriel's mind-reading

Galadriel tells Frodo and Sam that she knows Sauron's thoughts that concern the Elves.[17] It seems strange that they don't ask her whether she has any information they might find useful and she doesn't offer them any. Also, she doesn't seem to have known about Saruman's betrayal some nineteen years earlier, though the defection of a member of the White Council might be thought to concern the Elves. At least, she didn't warn Gandalf in the messages he got from Lórien after reading the Scroll of Isildur, the year before he trustingly entered Orthanc.[3] (Also, when Aragorn was serving in Gondor under the name Thorongil, he "often warned Ecthelion not to put trust in Saruman".[18] It's strange that he knew not to trust Saruman but Gandalf didn't.)

Explanation

Conceivably Galadriel gained the ability to read Sauron's mind sometime after the messages went to Gandalf.

Galadriel tells the Fellowship, "I will not give you counsel, saying do this, or do that. For not in doing or contriving, or in choosing between this course and another, can I avail; but only in knowing what was and is, and in part also what shall be."[19] Later she tells Frodo, "I do not counsel you one way or the other. I am not a counsellor."[17] However, the rhyme she sends Aragorn advises a specific course: the Grey Company should come out of Rivendell, and Aragorn should take the Paths of the Dead.[20] Likewise Legolas and Gimli conclude that Galadriel sent the message to the Grey Company telling them to join Aragorn in Rohan; this seems to be "contriving" and "choosing between one course and another". Incidentally, it is odd that the Grey Company got this message without knowing who it was from.[21]

Explanation

One could imagine that someone else (Celeborn?) made the decisions and Galadriel only sent the messages. Legolas and Gimli may have erred in thinking she was the source.

Tales of hobbits

Pippin tells Théoden, "I have wandered in many lands, since I left my home, and never till now have I found people that knew any story concerning hobbits."[4] But hobbits live in Bree, Tom Bombadil knows many stories about hobbits, one would think the Rangers (who guard the Shire and Bree) and the Elves of Rivendell (where Bilbo has been living) would know some, and the Elves of Lórien have at least heard of hobbits.[22]

Explanation

Pippin has just woken up from a nap, after a lunch that included wine, and is talking to a king for the first time in his life; he may not be thinking clearly.

Gandalf could have learned about the two palantíri by himself, after the last time the White Council met (66 years earlier), or he was concealing his knowledge so as to keep secret his source for this information.

The peril of deep arts

In connection with the palantír of Orthanc, Gandalf observes to Pippin, "Perilous to us all are the devices of an art deeper than we possess ourselves."[25] However, never in The Hobbit or The Lord of the Rings does he warn Thorin or the hobbits against using elvish swords, which glow in the presence of orcs, or daggers from the barrow, which are especially effective against Ringwraiths. He returns the Phial of Galadriel to Frodo and Galadriel's box of earth to Sam without any warnings. Also, there is no apparent danger in characters' using other products of elven arts (cloaks, hithlain ropes, lembas).

Explanation

Maybe the palantíri are "devices" in a sense in which the other things named are not.

Furthermore, it's possible that Gandalf was only attempting to discourage Pippin's curiosity, worrying that it could lead to another dangerous situation like that with the palantír.

The eyes in Orthanc

When Aragorn tells Gimli and Legolas that he's confronted Sauron in the palantír, he says, "To know that I lived and walked the earth was a blow to his heart, I deem; for he knew it not till now. The eyes in Orthanc did not see through the armour of Théoden".[26] But Wormtongue knew that Aragorn claimed to be Isildur's heir, as Gandalf points out to Pippin.[25] Thus whether Wormtongue recognized Aragorn from Orthanc doesn't matter to Sauron's knowledge of Aragorn's existence. What Aragorn should have deduced was that either Wormtongue never told Saruman about him, or Saruman didn't reveal the knowledge, whether to Sauron through the palantír or to the Nazgûl who came to demand Saruman's supposed captive hobbit. (The latter is what Gandalf tells Pippin he fears.)

Aragorn mentions that the name "Sauron" (meaning "Abominable") is the name used by his enemies, and Sauron himself does not permit it to be pronounced.[27] Therefore it would be problematic, if not logically impossible, for the messenger to Dáin to refer to his master as "the Lord Sauron the Great", as Aragorn had heard at the Council of Elrond,[28] and for a servant of Sauron to say, "I am the Mouth of Sauron".[29]

Explanation

It could be that Aragorn was mistaken, perhaps thinking of the time before Sauron had declared himself. Another possibility is that the "Mouth" used a different name or title, perhaps in the Black Speech, and Frodo or the translator Tolkien "translated" it as Sauron to clarify it for readers. A similar possibility is that despite Aragorn's blanket statement, Sauron sometimes allowed his servants to use the name for such purposes as communicating with others who used it.

Factual mistakes

The name Moria means "Black Chasm" and was a derogatory description of the place which the Dwarves did not like much; it was given after Durin's Bane took over the city and it was overrun by Orcs. It is therefore a paradox why that name appears on the Doors of Durin (Ennyn Durin Aran Moria), made in the Second Age, and with the consent of the Dwarves.

Explanation

An "external" explanation is that since the translated Norse names Durin and Narvi are seen in the inscription, Moria may also be a "translated" name.

One of the best-known alleged plot holes is why the Eagles came to carry Frodo and Sam back from Mount Doom but did not help them to fly the One Ring there. While there are many counter explanations, it is a logical gap that this idea was not proposed in the Council of Elrond.

Distances

The distances of the Dwarves' travel to Rivendell in The Hobbit seem to have different proportions than those in The Lord of the Rings. Tolkien tried to reconcile the Hobbit description with the scale of the LotR map but couldn't find an appropriate solution.[30]

The Orcs don't seem to react similarly in the sight of Glamdring in LotR, nor do they seem to recognize Narsil/Andúril, which is much more "recent".

Explanation

There can be several theories and explanations of how the swords and even their reputations reach Eriador. However, the narrative of The Silmarillion doesn't justify their significance to the extent of being remembered and recognized by the Goblins of the Third Age, even by tradition.

The sentence is somewhat ambiguous: "he" could refer to Bard or Girion instead of the elf-king. However, the elf-king's preference in gems, not the others', would be relevant to Bard's choice of what to give him.

It is difficult to reconcile the descriptions "beyond the Lune" and "in the south of the Ered Luin."

Other mentions of the Dwarves' homes in the Ered Luin are consistent with both possibilities. "Dwarves dwelt in the east side of the Blue Mountains, especially in those parts south of the Gulf of Lune, where they have mines that are still in use."[37] "Especially in those parts south of the Gulf of Lune" implies that a smaller number of Dwarves lived north of the Gulf, as shown in two other quotations. In a parenthetical comment made in "Of Dwarves and Men" in The Peoples of Middle-earth, Tolkien indicated that beyond the inflow of the Little Lune was 'Dwarf territory'.[38] Likewise in Appendix A: Arvedui, the last king of Arthedain, "hid in the tunnels of the old dwarf-mines near the far end of the Mountains".[37]

According to Appendix A, "The Stewards", during the Watchful Peace "Sauron withdrew before the power of the White Council and the Ringwraiths remained hidden in Morgul Vale". However the Watchful Peace ended in T.A.2460, three years before the White Council was formed. Thus according to Robert Foster, the reference to the Council is "incorrect".[40]

Explanation

Foster suggests that the reference to the "White Council" is rather to "the Wise" in general.

Moon phases

In general, it is possible that Tolkien consulted a modern almanac to model the moon phases, and also possible that he confused the meanings of "New Moon": the astronomical (the moment when the moon is darkest) and the colloquial (appearance of the new crescent moon).[41]

Another mistake appears in The Hobbit: Bard I killed Smaug "at the rising of the moon"[42] when "the moon rose above the eastern shore and silvered his [Smaug's] great wings... the waxing moon rose higher and higher". Also the thrush tells Bard, "Wait! Wait!... The Moon is rising." [43] However, according to astronomy a waxing moon rises only in the morning, after the sun. We can be certain the moon was waxing because this occurs the day after Durin's Day, which is the first day in the last month of autumn that the new moon is visible together with the sun.[44]

Explanation

One might imagine that Bard needed to wait for the moon to fall below a cloudbank and that the tradition is corrupt.[44]

Gandalf's letter

The letter Gandalf leaves for Frodo at the Prancing Pony is dated "Midyear's Day, Shire Year, 1418."[9] However, Appendix B says Gandalf met Radagast on June 29, and Gandalf says he left Bree at dawn of the following day,[3] which would be June 30, two days before Midyear's day (as 1 Lithe comes between).

Explanation

Possibly someone made a mistake involving the different calendars, though Bree uses the Shire-reckoning (aside from the number of the year). Perhaps more likely is that Gandalf, who was in a hurry, and traveling for days, confused the passage of time.

Shadow over Eregion

While the Fellowship of the Ring traverses Hollin, they see and feel a flying shadow over them.[15] Since no other such phenomena occur, when the Fell Beasts are introduced, the reader makes such a connection. However later we learn that Sauron did not permit the Nazgûl to traverse west of the Anduin after their accident at Bruinen.

Explanation

Possibly it was a "lost" or "disobeying" Nazgûl who despite orders found himself prematurely west of the Anduin, or simply something wholly unexplained and unrelated to the Fell Beasts. Perhaps it was some feeling of foreboding as they would eventually have to go to Moria.

Nights in Lórien

The surviving members of the Company spend their first night in Lórien in a "flet" in a tree. On their second night, "they rested and slept without fear on the ground".[45] On their third night, they sleep on the ground again, in a pavilion in Caras Galadon. "For a little while the travellers talked of their night before in the tree-tops, and of their day's journey...." And Aragorn says, "But tonight I shall sleep without fear for the first time since I left Rivendell."[46] The night in the tree-tops was not the night before, and Aragorn did sleep without fear on the previous night, so the second night appears to be forgotten.

The sapling's discovery

In the text of The Return of the King it is stated: "And Aragorn planted the new tree in the court by the fountain, and swiftly and gladly it began to grow; and when the month of June entered in it was laden with blossom".[47] The wording of this sentence suggests that Aragorn planted the sapling before June began. However, in Appendix B there is the entry: "June 25 (of 3019) King Elessar finds the sapling of the White Tree",[48] in which case it could not have blossomed until late in the month.